Motor vehicle bodywork, in particular in its body, includes parts that are tubular, in particular door and window bay risers, side rails, etc., which tubular parts constitute significant paths for propagating a variety of noises into the vehicle cabin, thereby reducing passenger comfort.
Providing sound insulation for such tubular parts thus raises a problem since such parts are of a variety of shapes and of varying section, and may themselves be constituted by assembling together a plurality of pieces.
In order to avoid noise propagation, motor vehicle manufacturers have, for a long time, been in the practice of closing the inside section of such tubular parts by locally injecting a composition that expands chemically and that serves to create a foam plug which comes into contact with the inside wall of such parts and which forms at least one sound insulating partition.
Foam is injected through a hole in the part, after the vehicle body has been painted. This solution applies when the part(s) (or the portion of a part) in which it is desired to provide a partition is itself a tube of right section that is substantially circular, and of diameter that is relatively small.
However, that solution requires the use of special equipment for injecting the foam.
Document U.S. Pat. No. 5,642,914 discloses a sound insulation device comprising a material that is expanded by applying heat and which is generally in the form of a flat ring that is fitted around the periphery of a partitioning insert. The ring is obtained by extrusion or by molding so as to give it the shape of the outline of the partitioning insert.
Document WO 01/83206 discloses a sound insulation device in which the thermally expandable material is molded on the periphery of a partitioning insert or is present in the form of a strip or a bead which is fixed to the periphery of said insert by adhesive or by means of staples.